(η6-Arene)ruthenium(II) complexes containing enantiomerically pure (β-aminoalkyl)phosphines or a (β-aminoalkyl) phosphinite: synthesis, stereochemical and kinetic studies
作者:Carmela G. Arena、Stefania Calamia、Felice Faraone、Claudia Graiff、Antonio Tiripicchio
DOI:10.1039/b003514i
日期:——
The chiral PâN* ligands [(S)-2-(dimethylamino)-3-phenylpropyl]diphenylphosphine, (S)-phephos, 1, [(S)-2-(dimethylamino)-2-phenylethyl]diphenylphosphine, (S)-phglyphos, 2, [(S)-2-(dimethylamino)-3-methylbutyl]diphenylphosphine, (S)-valphos, 3, and [(+)-(2S,3R)-4-(dimethylamino)-3-methyl]-2-diphenylphosphinoxy-1,2-diphenylbutane, (+)-(2S,3R)-chiraldphos, 4, reacted with [Ru(η6-arene)Cl2]2 (arene = p-cymene, benzene or hexamethylbenzene), in dichloromethane or tetrahydrofuran solution, affording the corresponding [Ru(η6-arene)(PâN*)Cl2] complexes, 5, in which the PâN* acts as a monodentate P-bonded ligand. In methanol the same reactions easily afforded the corresponding chelate complexes [Ru(η6-arene)(PâN*)Cl]Cl. Using ligands 1â3, when the arene is p-cymene, 90â¶10 diastereomeric mixtures of the cationic complexes have been obtained while only one diastereomer was formed in the corresponding reactions when the arene is benzene or hexamethylbenzene. The determination of the absolute configuration of the major products as RRu,SC diastereoisomers was made from the crystal structure and CD spectra comparison of the complex (RRu,SC)-[Ru(η6-p-MeC6H4Pri)(S-phglyphos)Cl]BF4. Complexes [Ru(η6-arene)(PâN*)Cl]Cl were also obtained by adding small amounts of methanol to solutions of [Ru(η6-arene)(PâN*)Cl2] in chloroform. A kinetic study, in CDCl3 solution containing variable amounts of methanol, on the chelation process in the neutral species [Ru(η6-arene)(PâN*)Cl2] showed first-order behaviour of the kobs values with the nucleophile (methanol) concentration. The pseudo-first-order rate constants are ascribed to replacement of Clâ by a molecule of methanol. A reaction mechanism is proposed.
手性 PâN* 配体[(S)-2-(二甲基氨基)-3-苯基丙基]二苯基膦,(S)-phephos,1,[(S)-2-(二甲基氨基)-2-苯基乙基]二苯基膦、(S)-phglyphos, 2, [(S)-2-(二甲基氨基)-3-甲基丁基]二苯基膦, (S)-valphos, 3, 和 [(+)-(2S,3R)-4-(二甲基氨基)-3-甲基]-2-二苯基膦氧基-1、在二氯甲烷或四氢呋喃溶液中,[(+)-(2S,3R)-chiraldphos, 4]与[Ru(δ-6-蒈烯)Cl2]2(蒈烯=对-甲苯、苯或六甲基苯)反应、得到相应的[Ru(δ-6-烯烃)(PâN*)Cl2]配合物 5,其中 PâN* 作为单价 P 键配体。在甲醇中,同样的反应很容易得到相应的螯合物 [Ru(δ-6-蒈烯)(PâN*)Cl]Cl。在使用配体 1â3 时,当烯烃为对-甲苯时,可以得到 90â¶10 个非对映异构体的阳离子络合物混合物,而当烯烃为苯或六甲基苯时,在相应的反应中只能形成一个非对映异构体。根据(RRu,SC)-[Ru(δ-6-p-MeC6H4Pri)(S-phglyphos)Cl]BF4 复合物的晶体结构和 CD 光谱比较,确定了主要产物为 RRu,SC 非对映异构体的绝对构型。在氯仿中的[Ru(δ-6-蒈烯)(PâN*)Cl2]溶液中加入少量甲醇,也可得到络合物[Ru(δ-6-蒈烯)(PâN*)Cl]Cl。在含有不同量甲醇的 CDCl3 溶液中,对中性物质 [Ru(δ-6-烯)(PâN*)Cl2]的螯合过程进行的动力学研究表明,kobs 值随亲核剂(甲醇)浓度的变化呈一阶行为。伪一阶速率常数归因于 Clâ 被一分子甲醇置换。提出了一种反应机理。